bonding of mono-tosyl-CD onto the surface of modified iron NPs by means of layerby-layer process [49–52]. Also, the one-pot route has been exploited to the preparation of CD-stabilized MNPs [56, 57]. Functionalized MNPs hold great potential in
environmental, biomedical, and clinical applications owing to their many unique
properties, such as larger surface area, and high permeability. In this part, we focus
on the recent advances in the construction of CD-functionalized MNPs and their
applications in identification-detection, adsorption-separation, and drug delivery.
15.3.1 Molecular Identification-Detection by Electrochemical and
Luminescent Sensors
MNPs have captured many interests in chemosensors for identification and detection
in terms of their high surface area, strong magnetic responsivity, electrical properties,
and high adsorption ability [58]. Cyclodextrins (CDs), as a group of naturally cyclic
oligosaccharides with a hydrophobic inner cavity and a hydrophilic exterior, may
bind selectively various organic, inorganic, and biological molecules to form complexes. Therefore, CD-coated MNPs have been investigated as promising method
for ion and molecular recognition by electrochemical sensing and spectral analysis
[59–62].
Electrochemical sensing that uses conjugates of MNPs with CDs constitutes an
emerging and widely explored area of molecular recognition research [52, 59–61].
Some bioactive species, like uric acid [49], dopamine [59], DNA [60], and amino
acids [52, 61], have been detected with excellent LOD values. Furthermore, due to
the CD cavity’s inherent chirality, electrochemical sensing of CD-MNPs for chiral
recognition has been also investigated. For instance, Muñoz et al. synthesized a
novel and specific material based on thiolated β-cyclodextrin-coated gold nanoparticle functionalized with cobalt ferrite magnetic nanoparticles (β-CDSH/Au/
CoFe 2 O 4 -NPs) for modifying on graphene-paste electrode (Fig. 5) [61]. The
β-CD-SH/Au/CoFe 2 O 4 -NP-modified graphene-paste electrode as a chiral sensor
has been validated by chirally recognizing tryptophan (TRP) enantiomers, showing
a good selectivity and sensitivity.
Spectrometry is another valid method to investigate the ion recognition by CDfunctionalized MNPs [53, 62]. Through the combination of the host-guest interaction and sol-gel grafting approach, a fluorescent TSRh6G-β-cyclodextrin
fluorophore/adamantane-functionalized magnetic nanoparticles (TFIC MNPs) has
been constructed as a fluorescence sensing platform for Hg
2+ recognition (Fig. 6)
[62]. The addition of Hg
2+ induced a remarkable emission enhancement of TFIC
MNPs as a “turn-on” type fluorescence sensor and resulted in an obvious color
change of the sample solution from light brown to pink. Due to the larger surface
area and high permeability, the CD hybrid nanomaterial TFIC MNPs displayed
significant selectivity and sensitivity for Hg
2+ over other metal ions tested in aqueous
solution. Otherwise, the TFIC MNPs could be separated and collected Hg
2+ via
external magnetic field, which can be used as an efficient adsorbent for the removal
of trace Hg
2+ from the aqueous environments.
15 Cyclodextrin Hybrid Inorganic Nanocomposites for Molecular Recognition. . .
435
environmental, biomedical, and clinical applications owing to their many unique
properties, such as larger surface area, and high permeability. In this part, we focus
on the recent advances in the construction of CD-functionalized MNPs and their
applications in identification-detection, adsorption-separation, and drug delivery.
15.3.1 Molecular Identification-Detection by Electrochemical and
Luminescent Sensors
MNPs have captured many interests in chemosensors for identification and detection
in terms of their high surface area, strong magnetic responsivity, electrical properties,
and high adsorption ability [58]. Cyclodextrins (CDs), as a group of naturally cyclic
oligosaccharides with a hydrophobic inner cavity and a hydrophilic exterior, may
bind selectively various organic, inorganic, and biological molecules to form complexes. Therefore, CD-coated MNPs have been investigated as promising method
for ion and molecular recognition by electrochemical sensing and spectral analysis
[59–62].
Electrochemical sensing that uses conjugates of MNPs with CDs constitutes an
emerging and widely explored area of molecular recognition research [52, 59–61].
Some bioactive species, like uric acid [49], dopamine [59], DNA [60], and amino
acids [52, 61], have been detected with excellent LOD values. Furthermore, due to
the CD cavity’s inherent chirality, electrochemical sensing of CD-MNPs for chiral
recognition has been also investigated. For instance, Muñoz et al. synthesized a
novel and specific material based on thiolated β-cyclodextrin-coated gold nanoparticle functionalized with cobalt ferrite magnetic nanoparticles (β-CDSH/Au/
CoFe 2 O 4 -NPs) for modifying on graphene-paste electrode (Fig. 5) [61]. The
β-CD-SH/Au/CoFe 2 O 4 -NP-modified graphene-paste electrode as a chiral sensor
has been validated by chirally recognizing tryptophan (TRP) enantiomers, showing
a good selectivity and sensitivity.
Spectrometry is another valid method to investigate the ion recognition by CDfunctionalized MNPs [53, 62]. Through the combination of the host-guest interaction and sol-gel grafting approach, a fluorescent TSRh6G-β-cyclodextrin
fluorophore/adamantane-functionalized magnetic nanoparticles (TFIC MNPs) has
been constructed as a fluorescence sensing platform for Hg
2+ recognition (Fig. 6)
[62]. The addition of Hg
2+ induced a remarkable emission enhancement of TFIC
MNPs as a “turn-on” type fluorescence sensor and resulted in an obvious color
change of the sample solution from light brown to pink. Due to the larger surface
area and high permeability, the CD hybrid nanomaterial TFIC MNPs displayed
significant selectivity and sensitivity for Hg
2+ over other metal ions tested in aqueous
solution. Otherwise, the TFIC MNPs could be separated and collected Hg
2+ via
external magnetic field, which can be used as an efficient adsorbent for the removal
of trace Hg
2+ from the aqueous environments.
15 Cyclodextrin Hybrid Inorganic Nanocomposites for Molecular Recognition. . .
435